Tān'ist, n.

n. [Ir. & Gael. tanaiste, tanaise, tanaistear, a lord or governor of a country, the presumptive or apparent heir to a prince, probably from Ir. tan, a country, territory. Cf. Gr. δυναστης, a lord, ruler.] A lord, or the proprietor of a tract of land, in Ireland; a governor or captain. This office or rank was elective, and often obtained by purchase or bribery.

This family [the O'Hanlons] were tanists of a large territory within the present county of Armagh. Lower.